The field of the present invention is separators for screening materials using vibratory motion for enhanced screening.
Vibratory separators have long been used for the multiple separation of materials, both wet and dry. The separators have been classically divided into rectangular screen separators and circular screen separators. An example of a rectangular screen separator is illustrated in U.S. Pat. No. 4,582,597 to Huber. This disclosed rectangular separator is particularly pertinent to the present invention and the disclosure thereof is incorporated herein by reference. A circular separator is illustrated in U.S. Pat. No. 4,613,432 to Racine et al., the disclosure of which is also incorporated herein by reference. Each type of separator has its own advantages well known in the industry.
The rectangular separator illustrated in U.S. Pat. No. 4,582,597 provides for advantageous mounting of rectangular screens. The device includes guideways for receiving the rectangular screens defined by an inflatable seal positioned under and displaced from a stop. The stop runs along two sides of the rectangular separator with the inflatable seal running along four sides. Thus, a screen mounted within the slot is constrained by two stops along opposite sides with a pneumatic seal extending about the full frame. This system allows for easy mounting with the inflatable seal in the deflated state and for sealing around the edges of the screen frame to avoid material bypassing the screen with the inflatable seal in the inflated condition.
The use of an inflatable seal system as in U.S. Pat. No. 4,582,597 has not been found advantageous in circular vibratory screen separators. Typically circular screen separators are built up by several sections which are stacked one upon another with screens located therebetween. The entire assembly is then securely clamped with clamp bands to hold the assembly together during vibration. An example of such construction is illustrated in U.S. Pat. No. 4,810,372 to Jones, the disclosure of which is incorporated herein by reference.
This stacked assembly has been found to allow access to the various screening levels. No means for positioning screens from the top without disassembling the separator housing has been found satisfactorily. Further, the clamp bands used on such stacked assemblies provide the structural support to withstand the induced vibrations. The tightening of such clamp bands, because of their angled channel structure, draws the stacked components together. This action compresses seals around screen frames to provide acceptable sealing against bypass flow. However, the use of clamp bands has become disfavored as assembly is convenient only with two or more operators helping to assemble or disassemble the separator housing.
The advantages of an inflatable seal system such as illustrated in U.S. Pat. No. 4,613,432 have not been realized in circular vibratory screen separators because of the need to rigidly hold the structure together. Far more rigid sealing gaskets are needed in the tight clamping of stacked components. An inflatable seal could not be involved in such clamping of components and, otherwise located, has been considered redundant.